1. Field of the Invention
This invention relates to systems for recycling or producing an element from feedstock material incorporating an oxide or alloy of the element. In particular this invention relates to apparatus and methods for producing high-purity magnesium from post-consumer scrap.
2. Background Information
Prompt and primary magnesium scrap are generally of a consistent chemistry with low oxide content, allowing them to be readily reused by die casting or strip casting. However, post-consumer magnesium scrap may include diverse alloy formulations and/or be highly oxidized, so that the magnesium is not recoverable in a useful form by such remelting-based methods, which are capable of diluting but not true refining. Thus, the presence of constituents deleterious to the mechanical properties of magnesium, for example, iron, nickel and chromium is not addressed by such treatments. Consequently, post-consumer magnesium scrap, such as the output from an automobile shredder, is not in general suitable for use in high-value products such as new automobiles after straightforward sorting and remelting.
Magnesium metal has a low density, with a high specific stiffness and specific strength. These attributes suit magnesium well for use in motor vehicles. U.S. automobile manufacturers project increasing in the average amount of magnesium used in cars and light trucks to 350 pounds per vehicle, compared to the current average of only about ten to fifteen pounds. Such expanded magnesium use, while desirable in some aspects, would likely create enormous landfill difficulties in the absence of a use for magnesium components at the end of a vehicle lifetime. There is, accordingly, a need for an economical and flexible approach to magnesium recycling.